TAILS 37 
so obvious. Take the lizard as an example. His tail 
would appear at first sight to be of little or no service 
to him, since he parts with it so readily. As a matter 
of fact, the little reptile has many enemies; of these, 
the Indian crow is the chief. Now, when a crow attacks 
a lizard, it naturally tries to seize him somewhere near 
the middle. While the bird is striking at him, the rep- 
tile starts to run away; the result is that the crow either 
misses him or seizes him by the tail. If the latter 
happens, the tail is swiftly detached, and the lizard 
makes good his escape. 
A few animals possess tails which apparently serve 
no useful purpose. These are exceedingly interesting 
creatures, for, if their tails really are useless, they are 
anomalies that threaten to upset all the theories of 
biological science. I do not know the use of the tail 
of the rat, or the mouse. Yet we may be tolerably 
certain that in each case the organ has some use or it 
would not exist. I employ the word “use” in a very 
wide sense. I hold an organ to be useful to an animal 
if it help its possessors to obtain a mate. 
Galton maintains that the action of Natural (or 
Sexual) Selection is necessary to keep any organ up 
to the mark; that if the action of Natural Selection 
is removed from any organ, that organ at once begins 
to deteriorate. In other words, from the moment an 
organ becomes useless to its possessor, that organ begins 
to degenerate, and eventually disappears. Proofs of 
this are seen throughout the realm of nature, 
Many animals which spend their lives in utter dark- 
ness, whether in the depths of the ocean, or in caves, 
